These studies will assess vasopressin's action on structural and functional properties of epithelial cell plasma membranes in the toad urinary bladder. (I plan to): 1. Delineate vasopression-induced alterations in the luminal membrane of toad urinary bladder and determine which membrane components mediate hormone-induced transport process using enzymatic and chemical probes. 2. Correlate the distribution of hormone receptors in intact epithelial cells with the response of these cells to vasopressin. 3. Improve methods for purifying and characterizing total, luminal, and basolateral plasma membranes. 4. Compare vasopressin-induced alterations in membrane conformation in whole bladder, intact cells and membrane fragments by spectroscopy.